Allow enabling raft NVTX markers when raft is installed (rapidsai#4718)

Adjust the name of the option according to the changes proposed in rapidsai/raft#610

Authors:
  - Artem M. Chirkin (https://github.com/achirkin)

Approvers:
  - Corey J. Nolet (https://github.com/cjnolet)

URL: rapidsai#4718

cpp/cmake/thirdparty/get_raft.cmake

@@ -62,7 +62,7 @@ function(find_and_configure_raft)
               "RAFT_COMPILE_NN_LIBRARY ${PKG_USE_RAFT_NN}"
               "RAFT_COMPILE_DIST_LIBRARY ${PKG_USE_RAFT_DIST}"
               "RAFT_USE_FAISS_STATIC ${PKG_USE_FAISS_STATIC}"
-              "NVTX ${NVTX}"
+              "RAFT_NVTX ${NVTX}"
     )
 
     if(raft_ADDED)